Image-taking apparatus

ABSTRACT

An image-taking apparatus is disclosed which has a mirror drive mechanism with a small number of constituent parts, easy assembly. The image-taking apparatus has a mirror movable to a first position in an optical path and to a second position outside the optical path, a first biasing member biasing the mirror from the second position to the first position, a second biasing member biasing the mirror from the first position to the second position, a holding member holding the first biasing member in a charged state, a first cam having a charge portion for charging the second biasing member and a release portion for releasing the charge of the second biasing member, a second cam releasing the holding by the holding member, and a motor driving both of the first and second cams only in one direction.

BACKGROUND OF THE INVENTION

The present invention relates to an image-taking apparatus which drivesa mirror which can move into and out of an image-taking optical path.

A mirror drive mechanism of a single-lens reflex camera has a motor, amirror drive cam gear having a cam portion, a mirror drive lever whichdrives the rotation of a movable mirror by the lift of the cam portionof the mirror drive cam gear, a shutter drive cam gear having a camportion, and a shutter drive lever which charges and drives a shutter bythe lift of the cam portion of the shutter drive cam gear (for example,see Japanese Patent Publication No. 7-27156).

In the drive mechanism, the mirror drive cam gear directly engages withthe shutter drive cam gear, and a transmission gear for transmitting thetorque of the motor in one direction engages with one of the cam gears.

The mirror drive cam gear, the shutter drive cam gear, and thetransmission gear which engages with one of the cam gears are arrangedsuch that they engage with each other in series. Thus, from theviewpoint of the other cam gear, the number of gear stages through whichthe motor driving force is transmitted is increased by one as comparedwith the one cam gear, so that the drive efficiency is not favorable.

In addition, since the mirror drive cam gear directly engages with theshutter drive cam gear, the cam gears rotate in opposite directions.This prevents an ideal arrangement of the rotational axes of the mirrordrive lever and the shutter drive lever in view of the drive efficiency.

The mirror drive cam gear directly engages with the shutter drive camgear and they occupy a pear-shaped space when viewed in the directionsof the rotational axes of the cam gears. It is thus impossible to placethe mirror drive lever and the shutter drive lever in an idealarrangement in view of their respective drive efficiencies, which isdisadvantageous in the drive efficiency and may increase the size of thecamera.

To address them, a drive mechanism has been disclosed in which a mirrortransmission gear engaging with a mirror drive cam gear and a shuttertransmission gear engaging with a shutter drive cam gear are disposedcoaxially and a transmission gear shaft driven by a motor is provided(for example, Japanese Patent Laid-Open No. 2002-23221). According tothe abovementioned structure, since the driving force of the motor isdirectly transmitted to the mirror drive cam gear and the shutter drivecam gear from the associated transmission gears, the difference in driveefficiency caused by the number of gear stages can be reduced ascompared with the structure in which the transmission gear engages onlywith the one of cam gears which engages with the other cam gear. Inaddition, the mirror drive cam gear and the shutter drive cam gear canbe rotated in the same direction to achieve an ideal arrangement of therotation axes of a mirror drive lever and a shutter drive lever in viewof the drive efficiency.

In the abovementioned mechanism, however, the number of parts isincreased, and a phase shift may occur in the mirror drive cam gear andthe shutter drive cam gear in assembly operation. Also, since the mirrordrive cam gear and the shutter drive cam gear are coupled through thetransmission gears, the backlash of the gears causes a phase shift, andthe rotation of one of the cam gears is feedback controlled, theinterlocking drive of a mirror and a shutter cannot be performed withhigh accuracy.

In the abovementioned two drive mechanisms, when the mirror is movedfrom within an image-taking optical path to the outside thereof, or whenthe mirror is moved into the image-taking optical path from the outsidethereof, the mirror is driven by the lift of the cam, so that the mirrordrive time is extended due to a change in voltage or the like.

Japanese Patent Laid-Open No. 1-134443 has disclosed a mirror drivemechanism which drives a mirror at high speed. The mirror drivemechanism is formed of a first engaging portion which positions themirror in an image-taking optical path, a first spring which urges themirror in a direction in which the mirror is moved out of theimage-taking optical path, a second engaging portion which positions themirror outside the image-taking optical path, and a second spring whichurges the mirror in a direction in which the mirror is moved into theimage-taking optical path, an electromagnet which releases theengagement in the first and second engaging portions, and a motor whichcharges the first and second springs.

While the mirror drive mechanism allows the high-speed drive of themirror, it needs a plurality of driving sources and a number of theconstituent parts, requiring extremely high cost. In addition, theelectromagnet has a finite releasing action on the engagement in theengagement portions and the positioning of the engagement portionscannot be enhanced.

Another image-taking apparatus has been disclosed which has a mirrordrive mechanism which utilizes the biasing force of a charged drivespring to allow a mirror to move into and out of an image-taking opticalpath and requires only one motor as a drive source (Japanese PatentLaid-Open No. 2002-174850).

In the abovementioned mechanism, the engagement of a raising lever needsto be released when the mirror is driven into the image-taking opticalpath from the outside thereof. Driving the motor for the engagementrelease simultaneously causes the charging of the spring for biasing themirror toward the outside of the image-taking optical path, therebyincreasing the load on the motor to take a long time for the engagementrelease.

The motor is rotated in different directions when the mirror is movedout of the image-taking optical path and when the mirror is moved intothe image-taking optical path. Since a mechanical lock is used toforcedly stop a cam gear in order to stop the rotation of the motor, ahigher mechanical load is applied.

Another mirror drive mechanism drives a charge lever by a cam gear afterthe completion of mirror drive operation to position an engaging portionof a hold lever provided for the charge lever to a claw portion of amirror lever. In the mechanism, however, the charge lever is driven athigh speed when the engaging portion of the hold lever is positioned tothe claw portion of the mirror lever, so that the end of the hold leverat high speed collides with the claw portion of the mirror lever. Thismay reduce the durability of the end of the hold lever and the clawportion of the mirror lever.

As a means for solving this, Japanese Patent Laid-Open No. 1-134443mentioned above has disclosed the structure in which the end of the holdlever is always in contact with the claw portion of the mirror lever toavoid a collision between the end of the hold lever and the claw portionof the mirror lever.

In the mechanism, however, the end of the hold lever is always in slidecontact with the claw portion of the mirror lever, so that the end ofthe hold lever needs to extend longer than the charge stroke of thecharge lever to cause an increased size of the camera.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide an image-takingapparatus, which has a mirror drive mechanism with a small number ofconstituent parts, easy assembly, and low cost.

According to an aspect, the present invention provides an image-takingapparatus comprising a mirror drive apparatus having a mirror, which ismovable to a first position at which the mirror is disposed in anoptical path and to a second position at which the mirror is retractedoutside the optical path, a first biasing member, which produces biasingforce for driving the mirror from the second position to the firstposition, a second biasing member, which produces biasing force fordriving the mirror from the first position to the second position, aholding member, which is allowed to hold the first biasing member in acharged state, a first cam, which has a charge portion for charging thesecond biasing member and a release portion for releasing the charge ofthe second biasing member, a second cam, which releases the holding bythe holding member, and a motor, which drives both of the first andsecond cams. The motor drives the first and second cams only in onedirection.

According to another aspect, the present invention provides animage-taking apparatus comprising a mirror, which is movable withrespect to an optical path, a mirror drive member, which is movable to afirst position at which the mirror is disposed in the optical path andto a second position at which the mirror is retracted outside theoptical path, a first biasing member, which produces biasing force fordriving the mirror drive member from the second position to the firstposition, a shutter, a shutter drive member, which drives the shutter, acoupling member, which is provided on the shutter drive member andcouples the mirror drive member to the shutter drive member, a secondbiasing member, which produces biasing force for driving the shutterdrive member and drives the mirror drive member from the first positionto the second position via the shutter drive member and the couplingmember, a first cam, which has a charge portion for driving the shutterdrive member in a direction in which the second biasing member ischarged and a release portion for allowing the drive of the shutterdrive member by the second biasing member, a second cam, which releasesthe coupling of the mirror drive member by the coupling member at thesecond position, and a motor which drives both of the first and secondcams. The motor drives the first and second cams only in one direction.

According to yet another aspect, the present invention provides animage-taking apparatus comprising a mirror, which is movable to a firstposition at which the mirror is disposed in an optical path and to asecond position at which the mirror is retracted outside the opticalpath, a first biasing member, which produces biasing force for drivingthe mirror from the second position to the first position, a secondbiasing member, which produces biasing force for driving the mirror fromthe first position to the second position, an engaging member, whichengages with the mirror to prevent the drive of the mirror by the firstbiasing member, a first cam, which includes a charge portion forcharging the second biasing member and a release portion for releasingthe charge of the second biasing member, and a second cam, whichreleases the engagement of the engaging member with the mirror. Thesecond cam causes the engaging member to retract from the mirror whenthe mirror and the engaging member are relatively moved toward aposition at which their engagement is allowed.

According to a further aspect, the present invention provides animage-taking apparatus comprising a mirror, which is movable to a firstposition at which the mirror is disposed in an optical path and to asecond position at which the mirror is retracted outside the opticalpath, a first biasing member, which produces biasing force for drivingthe mirror from the second position to the first position, a shutter, ashutter drive member, which drives the shutter, an engaging member,which is provided on the shutter drive member and engages with themirror, a second biasing member, which produces biasing force fordriving the shutter drive member and drives the mirror from the firstposition to the second position via the shutter drive member and theengaging member, a first cam, which includes a charge portion fordriving the shutter drive member in a direction in which the secondbiasing member is charged and a release portion for allowing the driveof the shutter drive member by the second biasing member, and a secondcam, which releases the engagement of the engaging member with themirror that has been moved to the second position. The second cam causesthe engaging member to retract from the mirror when the shutter drivemember is driven by the charge portion to a position at which theengagement of the engaging member and the mirror that has been moved tothe first position is allowed.

Other objects and features of the present invention will become readilyapparent from the following description of the preferred embodimentswith reference to accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a mirror box and the periphery in acamera which is Embodiment 1 of the present invention.

FIG. 2 is a perspective view showing the mirror box and the periphery inthe camera which is Embodiment 1.

FIG. 3 is an exploded perspective view showing the mirror box and theperiphery.

FIG. 4 shows a pattern on a phase detection substrate for detecting therotational phase of a cam gear in Embodiment

FIG. 5 shows a mirror drive cam and a hold release cam of the cam gearin Embodiment 1.

FIG. 6 is a side view showing a mirror drive mechanism when a movablemirror is at a viewfinder observing position and a shutter set member isat a charge complete position in Embodiment 1.

FIG. 7 is a side view showing the mirror drive mechanism when themovable mirror is at an image-taking position and the shutter set memberis at a charge release position in Embodiment 1.

FIG. 8 is a side view showing the mirror drive mechanism when themovable mirror is at the viewfinder observing position and the shutterset member is at the charge release position in Embodiment 1.

FIG. 9 shows the positions of the cam gear, a charge arm, and the holdrelease arm in the state of FIG. 6 when viewed from above the mirrorbox.

FIG. 10 shows the positions of the cam gear, the charge arm, and thehold release arm in the state of FIG. 7 when viewed from above themirror box.

FIG. 11 shows the positions of the cam gear, the charge arm, and thehold release arm in the state of FIG. 8 when viewed from above themirror box.

FIG. 12 shows a mirror drive cam and a hold release cam of a cam gear ina camera which is Embodiment 2 of the present invention.

FIG. 13 is a side view showing a mirror and shutter drive mechanism whena movable mirror is at a viewfinder observing position, a shutter setmember is moving to a charge complete position, and a hold lever is at aposition immediately before it engages with a mirror lever in Embodiment2.

FIG. 14 shows the positions of a cam gear, a charge arm, and a holdrelease arm in the state of FIG. 6 when viewed from above a mirror boxin Embodiment 2.

FIG. 15 shows the positions of the cam gear, the charge arm, and thehold release arm in the state of FIG. 7 when viewed from above themirror box in Embodiment 2.

FIG. 16 shows the positions of the cam gear, the charge arm, and thehold release arm in the state of FIG. 8 when viewed from above themirror box in Embodiment 2.

FIG. 17 shows the positions of the cam gear, the charge arm, and thehold release arm in the state of FIG. 13 when viewed from above themirror box in Embodiment 2.

FIG. 18 is a schematic diagram showing the camera of Embodiments 1 and2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will hereinafter bedescribed with reference to the drawings.

Embodiment 1

FIG. 18 schematically shows the structure of a single-lens reflexdigital camera (image-taking apparatus) which is Embodiment 1 (andEmbodiment 2 described later) of the present invention. In FIG. 18,reference numeral 201 shows a camera body and reference numeral 220shows an interchangeable lens which is mounted on the camera body 201.The interchangeable lens 220 has an image-taking optical systemconsisting of a plurality of lenses 221 and a stop, not shown, heldtherein. A mount 222 is fixed to the rear end of the interchangeablelens 220.

The camera body 201 has a mirror box 1 fixed therein. A mount 203 isfixed to the front of the mirror box 1 on which the mount 222 of theinterchangeable lens 220 is mounted through a bayonet mechanism, notshown. A movable mirror 2 is pivotally put in the mirror box 1. Themovable mirror 2 can be pivoted between a position at which it is placedin an optical path (image-taking optical path) of light from a subjectincident from the interchangeable lens 220 and to a position at which itis placed upward out of the optical path. When the movable mirror 2 isplaced in the image-taking optical path, it directs luminous flux fromthe interchangeable lens 220 to a viewfinder optical system 204 providedin an upper portion of the camera body 201 to allow an operator toobserve a subject. When the movable mirror 2 is moved to the position atwhich it is placed upward out of the optical path, it directs luminousflux from the interchangeable lens 220 toward an image-pickup device210, later described.

A focal plane shutter unit 205 is fixed to the rear end of the mirrorbox 1. The focal plane shutter unit 205 has a front curtain 205 a and arear curtain 205 b. When images are taken, the front curtain 205 a whichhas been closed travels in an open direction, and after a predeterminedtime period, the rear curtain 205 b which has been opened travels in aclose direction to shift a slit opening in parallel with alight-receiving surface of the image-pickup device 210 held in thecamera body 201, thereby performing exposure of the image-pickup device210.

The image-pickup device 210 is formed of a photoelectric conversiondevice such as a CCD sensor and a CMOS sensor. An image taken by theimage-pickup device 210 is recorded on a recording medium such as asemiconductor memory, not shown.

A display 215 for displaying images or the like taken by theimage-pickup device 210 is attached to the back of the camera body 210.

Description will hereinafter be made of the structure and operation of amirror drive mechanism which drives the movable mirror 2 and the shutterunit 205.

FIGS. 1 and 2 are perspective views showing the structure of the mirrorbox and the periphery in the camera of Embodiment 1. FIG. 3 is anexploded perspective view showing the structure of the mirror box andthe periphery.

In FIGS. 1 to 3, reference numeral 1 shows the mirror box, 2 the movablemirror, 3 a movable mirror drive spring (second biasing member), 4 amirror drive lever (mirror drive member), 5 a mirror drive lever returnspring, 6 a charge lever (driven member, shutter drive member), 7 a holdlever (engaging member), 8 a hold lever return spring, 9 a charge arm,10 a hold release arm, 11 a hold release arm return spring, 12 a camgear, 13 a phase detection contact, 14 a phase detection substrate, 15 afirst movable mirror return spring (first biasing member), 16 a secondmovable mirror return spring, 17 a motor, 18 a decelerating planetmechanism, 19 a flash unit drive gear, 20 a shutter set member, 22 amovable mirror drive spring fixing member, and 23 a hold lever shaft.

Description will be made of how to arrange and assemble theabovementioned parts.

The movable mirror 2 is held inside the mirror box 1 such that it can bepivoted upward and downward. Reference numeral 2 a shows a mirror drivepin which is formed integrally with the movable mirror 2 and protrudesout of the side of the mirror box 1 from the inside thereof. Referencenumeral 2 b shows a mirror return pin which is formed integrally withthe movable mirror 2 and protrudes out of the side of the mirror box 1from the inside thereof.

Reference numeral 1 a shows an opening which is formed in the side ofthe mirror box 1 and has an opening area larger than the operating areaof the mirror drive pin 2 a and the mirror return pin 2 b when viewed inthe axial direction of a shaft portion 1 b. Reference numeral 1 b showsthe shaft portion which rotatably holds the charge lever 6. Referencenumerals 1 c and 1 d show attaching portions which attach the firstmovable mirror return spring 15 and the second movable mirror returnspring 16, respectively.

Reference numeral 1 p shows a mirror up positioning portion which abutson the mirror drive lever 4 for positioning when the mirror is moved up.Reference numeral 1 q shows a mirror down positioning portion whichabuts on the mirror drive lever 4 for positioning when the mirror ismoved down. The shaft portion 1 b, the attaching portions 1 c, 1 d, andthe positioning portions 1 p, 1 q protrude from the side of the outsideof the mirror box and are formed integrally with the mirror box.

Reference numeral 6 a shows a shaft portion which is provided for thecharge lever 6 and rotatably holds the mirror drive lever 4 and aroundwhich a coil portion of the mirror drive lever return spring 5 is wound.Reference numeral 5 a shows a fixed end of the mirror drive lever returnspring 5 which is supported on a pole 1 e provided for the mirror box 1.Reference numeral 5 b shows a movable end of the mirror drive leverreturn spring 5 which is supported on a spring receiving portion 4 aprovided for the mirror drive lever 4. Thus, the mirror drive lever 4receives elastic force from the mirror drive lever return spring 5 andis urged in a counterclockwise direction.

A coil portion of the first movable mirror return spring 15 is woundaround the attaching portion 1 c of the mirror box 1. Reference numerals15 a and 15 b show a fixed end and a movable end of the first movablemirror return spring 15 which are supported on a pole 1 f provided forthe mirror box 1 and the mirror return pin 2 b provided for the movablemirror 2, respectively. Thus, the movable mirror 2 receives elasticforce from the first movable mirror return spring 15 and is driven to aviewfinder observing position.

After the attachment of the mirror drive lever 4 and the charge lever 6to the mirror box is finished, the fixing member 22 is attached to theend surface of the shaft portion 1 b. The movable mirror drive spring 3is wound around the fixing member 22.

Reference numeral 3 a shows a fixed end of the movable mirror drivingspring 3 which is supported on a pole 1 g provided for the mirror box 1.Reference numeral 3 b shows a movable end of the movable mirror drivespring 3 which is supported on a spring receiving portion 6 b providedfor the charge lever 6. Thus, the charge lever 6 receives elastic forcefrom the movable mirror drive spring 3 and is urged in a clockwisedirection (upward).

The movable mirror 2 can be moved into and out of the image-takingoptical path from the interchangeable lens mounted on the mount (203 inFIG. 18) attached to the front of the mirror box 1 to the image-pickupdevice disposed at the rear of the mirror box 1.

Specifically, the movable mirror 2 can be moved between the viewfinderobserving position at which it is placed across the image-taking opticalpath to reflect light from a subject to the viewfinder optical system(204 in FIG. 18) disposed in the upper portion of the mirror box 1 andan image-taking position at which it is placed out of the image-takingoptical path to direct light from a subject to the image-pickup device(210 in FIG. 18).

A drive pin abutting portion 4 b provided for the mirror drive lever 4abuts on the mirror drive pin 2 a provided for the movable mirror 2.Reference numeral 4 c shows a mirror drive lever engaging portion whichengages with a first hold lever engaging portion 7 a of the hold lever7. Reference numeral 4 d shows an abutting portion which abuts on anabutting portion 1 q provided for the mirror box 1.

A concave shutter charge portion 6 c provided for the charge lever 6pinches and holds a drive pin 20 a formed integrally with the shutterset member 20, later described. Reference numeral 6 d shows a chargelever engaging portion which engages with a charge arm engaging portion9 a of the charge arm 9, later described.

The hold lever 7 has the hold lever return spring 8 wound thereon and isrotatably supported by a hold lever attaching portion 6 e provided forthe charge lever 6 through the hold lever shaft 23. Reference numeral 8a shows a fixed end of the hold lever return spring which is supportedon a spring receiving portion 6 f provided for the charge lever 6.Reference numeral 8 b shows a movable end of the hold lever returnspring which is supported on a spring receiving portion 7 b provided forthe hold lever 7. Thus, the hold lever 7 receives elastic force from thehold lever return spring 8 and is urged in a clockwise direction.Reference numeral 7 c shows a second hold lever engaging portion whichengages with a hold release arm engaging portion 10 a provided for thehold release arm 10, later described.

The charge arm 9 is rotatably supported by a shaft portion 1 h providedfor the mirror box 1. Reference numeral 9 b shows a shaft portion whichrotatably holds the hold release arm 10, later described. A coil portionof the hold release arm return spring 11 is wound on the shaft portion 9b. Reference numeral 11 a shows a fixed end of the hold release armreturn spring 11 which is supported on a pile 1 i provided for themirror box 1. Reference numeral 11 b shows a movable end of the holdrelease arm return spring 11 which is supported on a spring receivingportion 10 b provided for the hold release arm 10. Thus, the holdrelease arm 10 receives elastic force from the hold release arm returnspring 11 and is urged in a counterclockwise direction when viewed fromabove the mirror box 1.

Reference numeral 9 c shows a cam pin provided for the charge arm 9which abuts on a charge cam 12 a (first cam) provided for the cam gear12. Reference numeral 10 c shows a cam pin provided for the hold releasearm which abuts on a hold release cam 12 b (second cam) provided for thecam gear 12.

The cam gear 12 is rotatably held by a shaft portion 1 j provided forthe mirror box 1. Thus, the charge cam 12 a and the hold release cam 12b are rotated around the shaft portion 1 j. A gear portion 12 c providedfor the cam gear 12 engages with a power transmission gear 18 a of thedecelerating planet mechanism 18, later described, and rotates in acounterclockwise direction when viewed from above the mirror box 1.

When the cam gear 12 starts rotation operation, the cam pin 9 c movesalong the outer shape of the charge cam 12 a provided for the cam gear12, and the charge arm 9 accordingly starts rotational reciprocationaround the shaft portion 1 h.

Since the cam pin 10 c similarly moves along the outer shape of the holdrelease cam 12 b provided for the cam gear 12, the hold release arm 10accordingly starts rotational reciprocation around the shaft portion 9b.

The phase detection contact 13 is fixed to the cam gear 12 with apredetermined phase relationship, and the contact 13 is in contact withthe pattern of the phase detection substrate 14, later described.

The phase detection substrate 14 is fixed with a predetermined phaserelationship to a gear hold cover, not shown, for holding the parts suchas the gears and arms attached to the mirror box 1 to prevent them fromcoming off the mirror box 1.

The decelerating planet mechanism 18 is rotatably attached to a shaftportion 1 n provided for the mirror box 1, decelerates and transmits thedriving force of the motor 17, and switches the transmission of thedriving force between the cam gear 12 and the flash unit drive gear 19,later described, in accordance with the rotation direction of the motor17. Reference numeral 18 c shows a power transmission gear whichtransmits the driving source to the flash unit drive gear 19 when themotor 17 is driven in the opposite direction to that in driving themirror.

The flash unit drive gear 19 is rotatably inserted into a hole portion 1o provided for the mirror box 1. The flash unit drive gear 19 transmitspower for open/close drive of a flash unit, not shown, or zoom drive. Itcan also transmit driving force to a mechanism other than the flashunit.

The shutter set member 20 is rotatably attached to a flange portion atthe rear end of the mirror box 1, and is rotated downward to move thefront curtain unit and the rear curtain unit of the focal plane shutter,not shown, in a charge direction. It is rotated upward from the chargecomplete state to a charge release state in which the charge of thefront curtain unit and the rear curtain unit can be released, so thatthe front curtain and the rear curtain travel from the state in whichthey are held in the charged state by an electromagnet, not shown, tocharge release of front and rear curtain drive springs by a controlunit, not shown, controlling the output from the electromagnet toprovide a predetermined shutter speed.

Next, description will be made of how to operate and control the mirrordrive mechanism with reference to FIGS. 4 to 11. FIG. 4 shows thepattern of the phase detection substrate 14 which detects the rotationalposition of the cam gear 12. FIG. 5 shows the phase relationship betweenthe charge cam 12 a and the hold release cam 12 b of the cam gear 12.FIG. 6 shows the mirror drive mechanism when the movable mirror 2 is atthe viewfinder observing position and the shutter set member 20 is atthe charge complete position, that is, an image-taking standby state.FIG. 7 shows the mirror drive mechanism when the movable mirror 2 is atthe image-taking position and the shutter set member 20 is at the chargerelease position, that is, a mirror up state. FIG. 8 shows the mirrordrive mechanism when the movable mirror 2 is at the viewfinder observingposition and the shutter set member 20 is at the charge releaseposition, that is, a mirror down state.

FIG. 9 shows the cam gear 12, the charge arm 9, and the hold release arm10 in the state shown in FIG. 6 viewed from above the mirror box 1. FIG.10 shows the cam gear 12, the charge arm 9, and the hold release arm 10in the state shown in FIG. 7 viewed from above the mirror box 1. FIG. 11shows the cam gear 12, the charge arm 9, and the hold release arm 10 inthe state shown in FIG. 8 viewed from above the mirror box 1.

First, description will be made of how to control the drive of the camgear 12 with reference to FIG. 4 showing the pattern of the phasedetection substrate 14. When the motor 17 is rotated in a predetermineddirection (for example, forward rotation), the driving force istransmitted to the gear portion 12 c of the cam gear 12 through thedecelerating planet mechanism 18 to rotate the cam gear 12 in onedirection in accordance with the predetermined direction. At this point,the phase detection contact 13 fixed to the cam gear 12 moves on thepattern of the phase detection substrate 14 in a counterclockwisedirection in FIG. 4.

The phase detection substrate 14 has three conductive patterns formedthereon, that is, a pattern 1 in accordance with a signal 1, a pattern 2in accordance with a signal 2, and a GND pattern. When the phasedetection contact 13 is located in the range of θ1 in which the pattern2 is connected to the GND pattern with no contact with the pattern 1,the state shown in FIG. 6 is entered, that is, the movable mirror 2 islocated in the image-taking optical axis at the viewfinder observingposition, and the shutter set member 20 is set to the charge completeposition.

When the phase detection contact 13 is located in the range of θ2 inwhich the pattern 1 is connected to the GND pattern with no contact withthe pattern 2, the movable mirror 2 is driven from the viewfinderobserving position toward the image-taking position outside theimage-taking optical path, and the shutter set member 20 is driven fromthe charge complete position toward the charge release position. Thus,the state shown in FIG. 7 is entered, that is, the movable mirror 2 andthe shutter set member 20 are set to the image-taking position and thecharge release position, respectively.

When the phase detection contact 13 is located in the range of θ3 inwhich none of the pattern 1 and the pattern 2 are in contact with theGND pattern, the movable mirror 2 is driven from the image-takingposition toward the viewfinder observing position. Thus, the state shownin FIG. 8 is entered, that is, the movable mirror 2 is set to theviewfinder observing position, and the shutter set member 20 remains inthe charge release position. The cam gear 12 continues the rotationoperation, and the mirror drive mechanism returns to the state shown inFIG. 6 from the state shown in FIG. 8.

An output signal from the phase detection substrate 14 is input to acontrol circuit, not shown. The control circuit operates to rotate themotor 17 from the rotational position of the cam gear 12 correspondingto the range of θ1 to the rotational position thereof corresponding tothe range of θ2 in accordance with the ON operation of a release switch,not shown, and stops the rotation of the motor 17 simultaneously withthe completion of the movement of the cam gear 12 to the positioncorresponding to the range of θ2.

Then, the control circuit controls the electromagnet, not shown, tocause the front curtain and the rear curtain, not shown, to travel, sothat a predetermined shutter speed is provided. After the exposuresequence of the shutter is finished, the control circuit operates torotate the motor 17 from the rotational position of the cam gear 12corresponding to the range of θ2 to the rotational position thereofcorresponding to the range of θ3, and to the rotational position thereofcorresponding to the range of θ1, thereby preparing for the nextimage-taking operation.

Next, description will be made of the phase relationship between thecharge gear 12 a and the hold release cam 12 b of the cam gear 12 withreference to FIG. 5 showing the cam lift arrangement of the cam gear 12of FIG. 5.

In FIG. 5, the upper cam shows the charge cam 12, while the lower camshows the hold release cam 12 b. The cam gear 12 is rotated in onedirection (counterclockwise direction) in response to the driving forceof the motor 17.

When the phase detection contact 13 is located in the range of θ1 on thepattern of the phase detection substrate 14, the abutting point of thecam pin 9 c of the charge arm 9 and the charge cam 12 a and the abuttingpoint of the cam pin 10 c of the hold release arm 10 and the holdrelease cam 12 b are located in the range of θ4.

The cam pin 9 c of the charge arm 9 abuts on a lift top surface 12 a 1of the charge cam 12 a. The cam pin 10 c of the hold release arm 10abuts on a lift bottom surface 12 b 2 of the hold release cam 12 b. Thecharge arm 9 and the hold release arm 10 are as shown in FIG. 9. Themirror drive mechanism is as shown in FIG. 6.

When the phase detection contact 13 is located in the range of θ2 on thepattern of the phase detection substrate 14, the abutting point of thecam pin 9 c of the charge arm 9 and the charge cam 12 a and the abuttingpoint of the cam pin 10 c of the hold release arm 10 and the holdrelease cam 12 b are located in the range of θ5.

The cam pin 9 c of the charge arm 9 abuts on a lift bottom surface 12 a2 of the charge cam 12 a. The cam pin 10 c of the hold release arm 10abuts on the lift bottom surface 12 b 2 of the hold release cam 12 b.The charge arm 9 and the hold release arm 10 are as shown in FIG. 10.The mirror drive mechanism is as shown in FIG. 7.

When the phase detection contact 13 is located in the range of θ3 on thepattern of the phase detection substrate 14, the abutting point of thecam pin 9 c of the charge arm 9 and the charge cam 12 a and the abuttingpoint of the cam pin 10 c of the hold release arm 10 and the holdrelease cam 12 b are located in the range of θ6.

Even when the cam gear 12 is further rotated to cause the cam pin 10 cof the hold release arm 10 to move from the lift bottom surface 12 b 2of the hold release cam 12 b of the cam gear 12 to a lift top surface 12b 1 and the cam pin 10 c moves in contact with the lift top surface 12 b1, the cam pin 9 c of the charge arm 9 remains in contact with the liftbottom surface 12 a 2 of the charge cam 12 a. The charge arm 9 and thehold release arm 10 are shown in FIG. 11, and the mirror drive mechanismis as shown in FIG. 8.

When the cam gear 12 is further rotated to the range of θ1, the chargearm 9 and the hold release arm 10 return to the state shown in FIG. 9,and the mirror drive mechanism returns to the state in FIG. 6, therebypreparing for the next image-taking operation.

Next, description will be made of the operation of the drive mechanismwhen the drive mechanism transitions from the state shown in FIGS. 6 and9 to the state shown in FIGS. 7 and 10.

In the state shown in FIG. 6, the charge lever 6 which drives theshutter member 20 is driven in the counterclockwise direction with thecharge arm engaging portion 9 a of the charge arm 9, so that the springreceiving portion 6 b of the charge lever 6 pushes the movable end 3 bof the movable mirror drive spring 3 to the right. Thus, the movablemirror drive spring 3 is charged to allow the drive of the charge lever6 in the clockwise direction and the shutter member 20 can be set to thecharge complete position. At this point, the first movable mirror returnspring 15 is not charged yet.

When the cam gear 12 is rotated in the counterclockwise direction fromthe abovementioned state in FIG. 9, the lift top surface 12 a 1 of thecharge cam 12 a which has abutted on the cam pin 9 c of the charge arm 9comes off, and the charge lever 6 is driven in the clockwise directionin FIG. 6 by the biasing force of the charged movable mirror drivespring 3. At this point, the charge lever engaging portion 6 b of thecharge lever 6 engages with the charge arm engaging portion 9 a of thecharge arm 9, so that the charge arm 9 is rotated in thecounterclockwise direction around the shaft portion 1 h of the mirrorbox 1 as shown in FIG. 10, and the cam pin 9 c of the charge arm 9 abutson the lift bottom surface 12 a 2 of the charge cam 12 a.

The driving of the charge lever 6 from the state shown in FIG. 6 to thestate shown in FIG. 7 causes the shutter charge portion 6 c of thecharge lever 6 to rotate upward the drive pin 20 a of the shutter setmember 20 pinched thereby to rotate the shutter set member 20 from thecharge complete position in FIG. 6 to the charge release position inFIG. 7.

The shutter set member 20 is rotated from the charge complete positionto the charge release position, and at the same time, the first holdlever engaging portion 7 a formed in the hold lever 7 engages with themirror drive lever engaging portion 4 c provided for the mirror drivelever 4 to couple the mirror drive lever 4 to the charge lever 6 anddrive the mirror drive lever 4 together with the charge lever 6 in theclockwise direction against the spring force of the mirror drive leverreturn spring 5.

The mirror drive lever 4 is rotated in the clockwise direction to causethe drive pin abutting portion 4 b of the mirror drive lever 4 to abuton the mirror drive pin 2 a of the movable mirror 2. Thus, the mirrordrive lever 4 rotates the movable mirror 2 from the viewfinder observingposition to the image-taking position shown in FIG. 7 through the mirrordrive pin 2 a. When an abutting portion 6 g of the charge lever 6 abutson the mirror up positioning portion 1 p of the mirror box 1, themovable mirror 2 reaches the image-taking position and the shutter setmember 20 reaches the charge release position as shown in FIG. 7.

In the state shown in FIG. 6, since the mirror return pin 2 b of themovable mirror 2 abuts on the movable end 15 b of the first movablemirror return spring 15, the movable mirror 2 is moved to theimage-taking position (moved upward) to charge the first movable mirrorreturn spring 15. In the state shown in FIG. 7, since the hold leverengaging portion 7 a of the hold lever 7 engages with the mirror drivelever engaging portion 4 c of the mirror drive lever 4, the mirror drivelever 4 can be prevented from rotation in the counterclockwise directionby the biasing force of the mirror drive lever return spring 5. As aresult, the first movable mirror return spring 15 can be held in acharged state.

Next, description will be made of the operation of the mirror drivemechanism when it transitions from the state shown in FIGS. 7 and 10 tothe state shown in FIGS. 8 and 11.

When the cam gear 12 is rotated in the counterclockwise direction fromthe state shown in FIG. 10, the cam pin 10 c of the hold release arm 10which has abutted on the lift bottom surface 12 b 2 of the hold releasecam 12 b of the cam gear 12 in FIG. 7 lies on and abuts on the lift topsurface 12 b 1 of the hold release cam 12 b. Since the cam pin 10 c ofthe hold release arm 10 moves from the lift bottom surface 12 b 2 of thehold release cam 12 b to the lift top surface 12 b 1, the hold releasearm 10 is rotated around the shaft portion 1 h of the mirror box 1 inthe clockwise direction and moved to the state shown in FIG. 11 againstthe biasing force of the hold release arm return spring 11.

The rotation of the hold release arm 10 in the clockwise directioncauses the hold release arm engaging portion 10 a of the hold releasearm 10 to move the second hold lever engaging portion 7 c of the holdlever 7 downward in FIG. 11.

The downward movement of the second hold lever engaging portion 7 c ofthe hold lever 7 in FIG. 11 causes the hold lever 7 to rotate in thecounterclockwise direction around the hold lever attaching portion 6 eof the charge lever 6 against the biasing force of the hold lever returnspring 8. When the cam gear 12 is rotated to the state shown in FIG. 11,the hold lever 7 is rotated to the state shown in FIG. 8.

When the hold lever 7 is rotated to the state shown in FIG. 8 in thismanner, the engagement of the hold lever 7 with the mirror drive lever 4is released. The mirror drive lever 4 is rotated in the counterclockwisedirection around the shaft portion 1b of the mirror box 1 by the biasingforce of the mirror drive lever return spring 5. After the start of therotation operation, the mirror drive lever 4 is rotated to the state inFIG. 8 in which it is stopped by the abutting portion 4 d abutting onthe mirror down positioning portion 1 q of the mirror box 1.

When the mirror drive lever 4 is rotated in the counterclockwisedirection, the mirror drive pin abutting portion 4 b which has abuttedon the mirror drive pin 2 a comes off. The movable mirror 2 is rotatedin the clockwise direction and is moved from the image-taking positionin FIG. 7 to the viewfinder observing position in FIG. 8 by the biasingforce of the charged first movable mirror return spring 15 and thesecond movable mirror return spring 16.

Next, description will be made of the operation of the mirror drivemechanism when it transitions from the state shown in FIGS. 8 and 11 tothe state shown in FIGS. 6 and 9.

When the cam gear 12 is rotated in the counterclockwise direction fromthe state shown in FIG. 11, the lift top surface 12 b 1 of the holdrelease cam 12 b of the cam gear 12 comes off, and the cam pin 10 c ofthe hold release arm 10 abuts on the lift bottom surface 12 b 2 of thehold release cam 12 b by the urge of the hold release arm return spring11. When the cam pin 10 c of the hold release arm 10 abuts on the liftbottom surface 12 b 2 of the hold release cam 12 b, the hold release arm10 is moved to the position in FIG. 9.

When the cam gear 12 is rotated in the counterclockwise direction fromthe state shown in FIG. 11, the cam pin 9 c of the charge arm 9 c whichhas abutted on the lift bottom surface 12 a 2 of the charge cam 12 a ofthe cam gear 12 abuts on the lift top surface 12 a 1 of the charge cam12 a. When the cam pin 9 c of the charge arm 9 moves to the lift topsurface 12 a 1 of the charge cam 12 a, the charge arm 9 is rotated andmoved to the position in FIG. 9.

When the charge is rotated in the counterclockwise direction, the chargearm engaging portion 9 a of the charge arm 9 engages with the chargelever engaging portion 6 d of the charge lever 6 to rotate the chargelever 6 in the counterclockwise direction. The counterclockwise rotationof the charge lever 6 charges the movable mirror drive spring 3 whosemovable ends 3 b and fixed end 3 a are supported on the spring receivingportion 6 b of the charge 7 lever 6 and the pole 1 g of the mirror box1, respectively.

Since the shutter charge portion 6 c of the charge lever 6 pushes downthe drive pin 20 a of the shutter set member 20 simultaneously, theshutter set member 20 is rotated toward the charge complete state shownin FIG. 6. When the cam pin 9 c of the charge arm 9 abuts on the lifttop surface 12 a 1 of the charge cam 12 a of the cam gear 12, theshutter set member 20 reaches the charge complete position, and theelectromagnet, not shown, holds the front curtain and the rear curtain,not shown, in the charge complete state by its absorption.

The first hold lever engaging portion 7 a of the hold lever 7 is inslide contact with the mirror drive lever engaging portion 4 c of themirror drive lever 4. As soon as the first hold lever engaging portion 7a is moved to the right of the mirror drive lever engaging portion 4 c,the hold lever 7 is rotated in the clockwise direction by the biasingforce of the hold lever return spring 8. Thus, the first hold leverengaging portion 7 a is pushed down, and as shown in FIG. 6, the firsthold lever engaging portion 7 a of the hold lever 7 is moved to theposition where it can lock the mirror drive lever engaging portion 4 cof the mirror drive lever 4.

In this manner, the state in FIG. 6 is moved to the state in FIG. 7, andto the state in FIG. 8, and returns to the state in FIG. 6. In otherwords, the cam gear 12 is rotated 360 degrees. Thus, one image-takingoperation is completed.

Since the rotation of the cam gear 12 in one direction can drive themovable mirror 2 and the shutter member 20, the drive control of themotor 17 can be simplified to realize the mirror drive mechanism bytaking account of load distribution.

Since the load distribution is considered, it is possible to provide themirror drive apparatus which consumes less power even when the samedriving force is used to drive the mirror and the shutter.

The charge cam 12 a and the hold release cam 12 b are formed of onemember and they are driven in one direction around the same axis toallow the driving of the drive mechanism for the mirror and the shutter.Thus, high drive efficiency is achieved, and a phase shift between twocams due to assembly errors can be prevented. As a result, it ispossible to provide the mirror drive apparatus with less powerconsumption and high accuracy.

In this manner, according to Embodiment 1, the motor can drive the firstand second cams only on direction to move the mirror to the first andsecond positions. Thus, when the driving force of the motor rotated inthe other direction can be applied to driving of another drive mechanism(for example, driving of the flash unit, driving of load/unload of arecording medium, and driving of film feed and driving of load/unload ofa film cartridge for a film camera). Consequently, driving the otherdrive mechanism does not need the use of another motor, thereby makingit possible to provide the mirror drive apparatus which has a smallernumber of constituent parts, allows easy assembly, and requires lowcost.

Embodiment 2

Description will hereinafter be made of the structure of a single-lensreflex digital camera which is Embodiment 2 of the present invention.The basic structure and operation of the camera of Embodiment 2 are thesame as those described in Embodiment 1 with reference to FIGS. 1 to 4and FIGS. 6 to 8. Thus, the common structure will be described withreference to the same drawings or omitted. In Embodiment 2, the shape ofa cam gear 12′ shown in FIG. 12 differs from that of the cam gear 12 inEmbodiment 1. In FIGS. 4 and 6 to 8, the cam gear 12 can be regarded asthe cam gear 12′.

Description will be made of how to operate and control a mirror andshutter drive mechanism with reference to FIGS. 4, 6 to 8, and 12 to 17.FIG. 4 shows the pattern of a phase detection substrate 14 which detectsthe rotational position of the cam gear 12′. FIG. 6 shows the mirror andshutter drive mechanism when a movable mirror 2 is at a viewfinderobserving position and a shutter set member 20 is at a charge completeposition, that is, an image-taking standby state.

FIG. 7 shows the mirror and shutter drive mechanism when the movablemirror 2 is at an image-taking position and the shutter set member 20 isat a charge release position, that is, a mirror up state. FIG. 8 showsthe mirror and shutter drive mechanism when the movable mirror 2 is atthe viewfinder observing position and the shutter set member 20 is atthe charge release position, that is, a mirror down state. FIG. 13 showsthe mirror and shutter drive mechanism when the movable mirror 2 is atthe viewfinder observing position, the shutter set member 20 is beingcharged, and a hold lever 7 is in a state immediately before it engageswith a mirror drive lever.

FIG. 14 shows the cam gear 12′, a charge arm 9, and a hold release arm10 in the state shown in FIG. 6 viewed from above a mirror box 1. FIG.15 shows the cam gear 12′, the charge arm 9, and the hold release arm 10in the state shown in FIG. 7 viewed from above the mirror box 1. FIG. 16shows the cam gear 12′, the charge arm 9, and the hold release arm 10 inthe state shown in FIG. 8 viewed from above the mirror box 1. FIG. 17shows the cam gear 12′, the charge arm 9, and the hold release arm 10 inthe state shown in FIG. 13 viewed from above the mirror box 1. FIG. 12shows the phase relationship between a charge cam 12 a′ of the cam gear12′ and a hold release cam 12 b′.

First, description will be made of how to control the driving of the camgear 12′ with reference to FIG. 4 showing the pattern of the phasedetection substrate 14. When a motor 17 is rotated in a predetermineddirection (for example, forward rotation), the driving force istransmitted to a gear portion 12 c′ of the cam gear 12′ through adecelerating planet mechanism 18 to rotate the cam gear 12′ in onedirection in accordance with the predetermined direction. At this point,a phase detection contact 13 fixed to the cam gear 12′ moves on thepattern of the phase detection substrate 14 in a counterclockwisedirection in FIG. 4.

The phase detection substrate 14 has three conductive patterns formedthereon, that is, a pattern 1 in accordance with a signal 1, a pattern 2in accordance with a signal 2, and a GND pattern. When the phasedetection contact 13 is located in the range of θ1 in which the pattern2 is connected to the GND pattern with no contact with the pattern 1,the state shown in FIG. 6 is entered, that is, the movable mirror 2 islocated in an image-taking optical axis at the viewfinder observingposition, and the shutter set member 20 is set to the charge completeposition.

When the phase detection contact 13 is located in the range of θ2 inwhich the pattern 1 is connected to the GND pattern with no contact withthe pattern 2, the movable mirror 2 is driven from the viewfinderobserving position toward the image-taking position outside theimage-taking optical path, and the shutter set member 20 is driven fromthe charge complete position toward the charge release position. Thus,the state shown in FIG. 7 is entered, that is, the movable mirror 2 andthe shutter set member 20 are set to the image-taking position and thecharge release position, respectively.

When the phase detection contact 13 is located in the range of θ3 inwhich none of the pattern 1 and the pattern 2 are in contact with theGND pattern, the movable mirror 2 is driven from the image-takingposition toward the viewfinder observing position. Thus, the state shownin FIG. 8 is entered, that is, the movable mirror 2 is set to theviewfinder observing position, and the shutter set member 20 remains inthe charge release position.

The cam gear 12 continues the rotation operation, and the mirror andshutter drive mechanism moves from the state shown in FIG. 8 to thestate shown in FIG. 13, that is, the state during the charging of theshutter set member 20 to the charge complete position and immediatelybefore the engagement of the hold lever 7 with the mirror drive lever 4.In addition, the state is moved to the state shown in FIG. 6, that is,the image-taking standby state in which the shutter set member 20 ismoved to the charge complete position and the hold lever 7 is engageablewith the mirror drive lever 4.

An output signal from the phase detection substrate 14 it input to acontrol circuit, not shown. The control circuit operates to rotate themotor 17 from the rotational position of the cam gear 12′ correspondingto the range of θ1 to the rotational position thereof corresponding tothe range of θ2 in accordance with the ON operation of a release switch,not shown, and stops the rotation of the motor 17 simultaneously withthe completion of the movement of the cam gear 12′ to the positioncorresponding to the range of θ2.

Then, the control circuit controls the electromagnet, not shown, tocause the front curtain (205 a in FIG. 18) and the rear curtain (205 bin FIG. 18) to travel, so that a predetermined shutter speed isprovided. After the exposure sequence of the shutter is finished, thecontrol circuit drives the motor 17 to rotate from the rotationalposition of the cam gear 12′ corresponding to the range of θ2 to therotational position thereof corresponding to the range of θ3, and to therotational position thereof corresponding to the range of θ1, therebypreparing for the next image-taking operation.

Next, description will be made of the phase relationship between thecharge gear 12 a′ and the hold release cam 12 b′ of the cam gear 12′with reference to FIG. 12 showing the cam lift arrangement of the camgear 12′.

In FIG. 12, the upper cam shows the charge cam 12 a′, while the lowercam shows the hold release cam 12 b′. The cam gear 12′ is rotated in onedirection (counterclockwise direction) in response to the driving forceof the motor 17.

When the phase detection contact 13 is located in the range of θ1 on thepattern of the phase detection substrate 14, the abutting point of a campin 9 c of the charge arm 9 and the charge cam 12 a′ and the abuttingpoint of a cam pin 10 c of the hold release arm 10 and the hold releasecam 12 b are located in the range of θ4.

The cam pin 9 c of the charge arm 9 abuts on a lift top surface 12 a 1′of the charge cam 12 a′. The cam pin 10 c of the hold release arm 10abuts on a lift bottom surface 12 b 2′ of the hold release cam 12 b′.The charge arm 9 and the hold release arm 10 are as shown in FIG. 14.The mirror and shutter drive mechanism is as shown in FIG. 6.

When the phase detection contact 13 is located at a rotational positionin the range of θ2 on the pattern of the phase detection substrate 14,the abutting point of the cam pin 9 c of the charge arm 9 and the chargecam 12 a′ and the abutting point of the cam pin 10 c of the hold releasearm 10 and the hold release cam 12 b′ are located in the range of θ5.

The cam pin 9 c of the charge arm 9 abuts on a lift bottom surface 12 a2′ of the charge cam 12 a′. The cam pin 10 c of the hold release arm 1abuts on the lift bottom surface 12 b 2′ of the hold release cam 12 b′.The charge arm 9 and the hold release arm 10 are as shown in FIG. 15.The mirror and shutter drive mechanism is as shown in FIG. 7.

When the phase detection contact 13 is located in the range of θ3 on thepattern of the phase detection substrate 14, the abutting point of thecam pin 9 c of the charge arm 9 and the charge cam 12 a′ and theabutting point of the cam pin 10 c of the hold release arm 10 and thehold release cam 12 b′ are located in the range of θ6.

Even when the cam gear 12′ is further rotated to cause the cam pin 10 cof the hold release arm 10 to move from the lift bottom surface 12 b 2′of the hold release cam 12 b′ of the cam gear 12′ to a lift top surface12 b 1′and the cam pin 10 c moves in contact with the lift top surface12 b 1′, the cam pin 9 c of the charge arm 9 remains in contact with thelift bottom surface 12 a 2′ of the charge cam 12 a′. The charge arm 9and the hold release arm 10 are shown in FIG. 16, and the mirror andshutter drive mechanism is as shown in FIG. 8.

When the cam gear 12′ is further rotated, the cam pin 9 c of the chargearm 9 abuts on a lift surface 12 a 3′ of the charge cam 12 a′, and thecam pin 10 c of the hold release arm 10 abuts on a charge lift surface12 b 3′ of the hold release cam 12 b′. The charge arm 9 and the holdrelease arm 10 are shown in FIG. 17, and the mirror and shutter drivemechanism is shown in FIG. 13.

When the cam gear 12′ is further rotated to the range of θ1, the chargearm 9 and the hold release arm 10 return to the state shown in FIG. 14,and the mirror and shutter drive mechanism returns to the state in FIG.6, thereby preparing for the next image-taking operation.

Next, description will be made of the operation when the mirror andshutter drive mechanism transitions from the state shown in FIGS. 6 and14 to the state shown in FIGS. 7 and 15.

In the state shown in FIG. 6, a charge lever 6 which drives the shuttermember 20 is driven in the counterclockwise direction with a charge armengaging portion 9 a of the charge arm 9, so that a spring receivingportion 6 b of the charge lever 6 pushes a movable end 3 b of a movablemirror drive spring 3 to the right. Thus, the movable mirror drivespring 3 is charged to allow the drive of the charge lever 6 in theclockwise direction and the shutter member 20 can be set to the chargecomplete position. At this point, a first movable mirror return spring15 is not charged yet.

When the cam gear 12′ is rotated in the counterclockwise direction fromthe abovementioned state in FIG. 14, the lift top surface 12 a 1′ of thecharge cam 12 a′ which has abutted on the cam pin 9 c of the charge arm9 comes off, and the charge lever 6 is driven in the clockwise directionin FIG. 6 by the biasing force of the charged movable mirror drivespring 3. At this point, a charge lever engaging portion 6 d of thecharge lever 6 engages with the charge arm engaging portion 9 a of thecharge arm 9, so that the charge arm 9 is rotated in thecounterclockwise direction around a shaft portion 1 h of the mirror box1 as shown in FIG. 15, and the cam pin 9 c of the charge arm 9 abuts onthe lift bottom surface 12 a 2′ of the charge cam 12 a′.

The charge arm 9 enters the state in FIG. 11 to cause the charge lever 6urged in the clockwise direction by the movable mirror drive spring 3 inFIG. 6 to be rotated in the clockwise direction around a shaft portion 1b of the mirror box 1.

The movement of the charge lever 6 from the state shown in FIG. 6 to thestate shown in FIG. 7 causes a shutter charge portion 6 c of the chargelever 6 to rotate upward a drive pin 20 a of the shutter set member 20pinched thereby to rotate the shutter set member 20 from the chargecomplete position in FIG. 6 to the charge release position in FIG. 7.

The shutter set member 20 is rotated from the charge complete positionto the charge release position, and at the same time, a first hold leverengaging portion 7 a formed in the hold lever 7 engages with a mirrordrive lever engaging portion 4 c provided for the mirror drive lever 4to couple the mirror drive lever 4 to the charge lever 6 and drive themirror drive lever 4 together with the charge lever 6 in the clockwisedirection against the spring force of the mirror drive lever returnspring 5.

The mirror drive lever 4 is rotated in the clockwise direction to causea drive pin abutting portion 4 b of the mirror drive lever 4 to abut ona mirror drive pin 2 a of the movable mirror 2. Thus, the mirror drivelever 4 rotates the movable mirror 2 from the viewfinder observingposition to the image-taking position shown in FIG. 7 through the mirrordrive pin 2 a. When an abutting portion 6 g of the charge lever 6 abutson a mirror up positioning portion 1 p of the mirror box 1, the movablemirror 2 reaches the image-taking position and the shutter set member 20reaches the charge release position as shown in FIG. 7. In the stateshown in FIG. 6, since a mirror return pin 2 b of the movable mirror 2abuts on a movable end 15 b of the first movable mirror return spring15, the movable mirror 2 is moved to the image-taking position (movedupward) to charge the first movable mirror return spring 15.

In the state shown in FIG. 7, since the hold lever engaging portion 7 aof the hold lever 7 engages with the mirror drive lever engaging portion4 c of the mirror drive lever 4, the mirror drive lever 4 can beprevented from rotation in the counterclockwise direction by the biasingforce of the mirror drive lever return spring 5. As a result, the firstmovable mirror return spring 15 can be held in a charged state.

Next, description will be made of the operation of the mirror andshutter drive mechanism when the state shown in FIGS. 7 and 15 is movedto the state shown in FIGS. 8 and 16.

When the cam gear 12′ is rotated in the counterclockwise direction fromthe state shown in FIG. 15, the cam pin 10 c of the hold release arm 10which has abutted on the lift bottom surface 12 b 2′ of the hold releasecam 12 b′ of the cam gear 12′ in FIG. 7 lies on and abuts on the lifttop surface 12 b 1′ of the hold release cam 12 b′. Since the cam pin 10c of the hold release arm 10 moves from the lift bottom surface 12 b 2′of the hold release cam 12 b′ to the lift top surface 12 b 1′, the holdrelease arm 10 is rotated around the shaft portion 1 h of the mirror box1 in the clockwise direction and moved to the state shown in FIG. 16against the biasing force of the hold release arm return spring 11.

The rotation of the hold release arm 10 in the clockwise directioncauses a hold release arm engaging portion 10 a of the hold release arm10 to move a second hold lever engaging portion 7 c of the hold lever 7downward in FIG. 16.

The downward movement of the second hold lever engaging portion 7 c ofthe hold lever 7 in FIG. 16 causes the hold lever 7 to rotate in thecounterclockwise direction around a hold lever attaching portion 6 e ofthe charge lever 6 against the biasing force of a hold lever returnspring 8. When the cam gear 12′ is rotated to the state shown in FIG.16, the hold lever 7 is rotated to the state shown in FIG. 8.

When the hold lever 7 is rotated to the state shown in FIG. 8 in thismanner, the engagement of the hold lever 7 with the mirror drive lever 4is released. The mirror drive lever 4 is rotated in the counterclockwisedirection around the shaft portion 1 b of the mirror box 1 by thebiasing force of the mirror drive lever return spring 5. After the startof the rotational operation, the mirror drive lever 4 is rotated to thestate in FIG. 8 in which it is stopped by an abutting portion 4 dabutting on a mirror down positioning portion 1 q of the mirror box 1.

When the mirror drive lever 4 is rotated in the counterclockwisedirection, the mirror drive pin abutting portion 4 b which has abuttedon the mirror drive pin 2 a comes off. The movable mirror 2 is rotatedin the clockwise direction and is moved from the image-taking positionin FIG. 7 to the viewfinder observing position in FIG. 8 by the biasingforce of the charged first movable mirror return spring 15 and thesecond movable mirror return spring 16.

Next, description will be made of the operation of the mirror andshutter drive mechanism when it transitions from the state shown inFIGS. 8 and 16 to the state shown in FIGS. 13 and 17.

When the cam gear 12′ is further rotated in the counterclockwisedirection from the state shown in FIG. 16, the cam pin 9 c which hasabutted on the lift bottom surface 12 a 2′ of the charge cam 12 a′ abutson the lift surface 12 a 3′ of the charge cam 12 a′, and the cam pin 10c which has abutted on the lift top surface 12 b 1′ of the hold releasecam 12 b′ abuts on the charge lift surface 12 b 3′ of the hold releasecam 12 b′.

Since the cam pin 9 c abuts on the lift surface 12 a 3′ of the chargecam 12 a′, the charge arm 9 is driven and rotated to the position inFIG. 17.

Since the cam pin 10 c abuts on the charge lift surface 12 b 3′ of thehold release cam 12 b′, the hold release arm 10 is drive and rotated tothe position in FIG. 17.

When the charge arm 9 is rotated in the clockwise direction, the chargearm engaging portion 9 a engages with the charge lever engaging portion6 d to cause the charge lever 6 to be rotated in the counterclockwisedirection when viewed in the axis direction of the shaft portion 1 b.The counterclockwise rotation of the charge lever 6 charges the movablemirror drive spring 3 whose movable ends 3 b and fixed end 3 a aresupported on the spring receiving portion 6 b of the charge lever 6 anda pole 1 g of the mirror box 1, respectively.

When the hold release arm 10 is rotated in the clockwise direction, thehold release arm engaging portion 10 a abuts on the second hold leverengaging portion 7 c and push it to the right, so that the hold lever 7is rotated in the counterclockwise direction around the shaft portion 6e when the charge lever 6 is rotated in the counterclockwise direction.

Since the hold lever 7 is driven in the counterclockwise directionaround the shaft portion 6 e in this manner, the hold lever 7 can beretracted to the position at which the end of the first hold leverengaging portion 7 a does not collide with the mirror drive leverengaging portion 4 c when the charge lever 6 is rotated to the state inFIG. 13. Thus, the collision between the mirror drive lever engagingportion 4 c and the first hold lever engaging portion 7 a can be avoidedto enhance the durability of the mirror drive lever 4 and the hold lever7. As a result, it is possible to provide a durable camera.

In addition, since the shutter charge portion 6 c of the charge lever 6pushes down the drive pin 20 a of the shutter set member 20, the shutterset member 20 is rotated to the state shown in FIG. 13.

Next, description will be made of the operation of the mirror andshutter drive mechanism when it transitions from the state shown inFIGS. 13 and 17 to the state shown in FIGS. 6 and 14.

When the cam gear 12′ is rotated in the counterclockwise direction fromthe state shown in FIG. 17, a charge lift top surface 12 b 4′ of thehold release cam 12 b′ comes off. Since the hold release arm 10 is urgedby the hold release arm return spring 11 for rotation in the clockwisedirection, the cam pin 10 c abuts on the lift bottom surface 12 b 2′ ofthe hold release cam 12 b′.

When the cam pin 10 c abuts on the lift bottom surface 12 b 2′ of thehold release cam 12 b′, the hold release arm 10 is moved to the positionin FIG. 14. When the hold release arm 10 reaches the position in FIG.14, the engagement of the hold lever 7 with the hold release arm 10 isreleased, and as shown in FIG. 6, the first hold lever engaging portion7 a is moved in contact with the mirror drive lever engaging portion 4c. When the contact of the first hold lever engaging portion 7 a withthe mirror drive lever engaging portion 4 c is broken, the hold lever 7receiving the biasing force from the hold lever return spring 8 startsrotation operation in the clockwise direction to push down the firsthold lever engaging portion 7 a. As a result, the first hold leverengaging portion 7 a is moved to the position at which it locks themirror drive lever engaging portion 4 c as shown in FIG. 6.

When the cam gear 12′ is rotated in the counterclockwise direction fromthe state shown in FIG. 17, the cam pin 9 c which has abutted on thecharge lift surface 12 a 3′ of the charge cam 12 a′ of the cam gear 12′abuts on the lift top surface 12 a 1′ of the charge cam 12 a′. As thecam pin 9 c moves on the lift top surface 12 a 1′ of the charge cam 12a′, the charge arm 9 is driven and rotated to the position in FIG. 14.

When the charge arm 9 is further rotated in the clockwise direction fromthe state, the charge lever 6 is further rotated in the counterclockwisedirection since the charge arm engaging portion 9 a engages with thecharge lever engaging portion 6 d. The counterclockwise rotation of thecharge lever 6 fully charges the movable mirror drive spring 3 whosemovable ends 3 b and fixed end 3 a are supported on the spring receivingportion 6 b of the charge lever 6 and a pole 1 g of the mirror box 1,respectively.

Simultaneously, the shutter charge portion 6 c pushes down the drive pin20 a of the shutter set member 20, so that the shutter set member 20 isrotated toward the charge complete position shown in FIG. 6. When thecam pin 9 c abuts on the lift top surface 12 a 1′ of the charge cam 12a′, the charge of the shutter set member 20 is completed, and theelectromagnet, not shown, holds the front curtain (205 a in FIG. 18) andthe rear curtain (205 b in FIG. 18) in the charge complete state by itsabsorption.

In this manner, the state in FIG. 6 is moved to the state in FIG. 7, tothe state in FIG. 8, and to the state in FIG. 13, and returns to thestate in FIG. 6. In other words, the cam gear 12′ is rotated 360degrees. Thus, one image-taking operation is completed.

According to Embodiment 2, since the engaging member can be retractedfrom the mirror in the relative movement of the mirror and the engagingmember toward the position at which they can engage, the collisionbetween the engaging member and the mirror can be avoided.

In addition, since the second cam which releases the engagement of theengaging member with the mirror is used to retract the engaging memberfrom the mirror, it is possible to avoid collision between the engagingmember and the mirror without adding a new part. Thus, the image-takingapparatus can be reduced in size.

This application claims foreign priority benefits based on JapanesePatent Applications Nos. 2004-173600, filed on Jun. 11, 2004, and2004-177543, filed on Jun. 15, 2004, and each of which is herebyincorporated by reference herein in its entirety as if fully set forthherein.

1. An image-taking apparatus having a mirror drive apparatus comprising:a mirror, which is movable to a first position at which the mirror isdisposed in an optical path and to a second position at which the mirroris retracted from the optical path; a first biasing member, whichproduces biasing force for driving the mirror from the second positionto the first position; a second biasing member, which produces biasingforce for driving the mirror from the first position to the secondposition; a holding member, which is allowed to hold the first biasingmember in a charged state; a first cam, which includes a charge portionfor charging the second biasing member and a release portion forreleasing the charge of the second biasing member; a second cam, whichreleases the holding by the holding member; and a motor, which drivesboth of the first and second cams, wherein the motor drives the firstand second cams only in one direction.
 2. The image-taking apparatusaccording to claim 1, wherein the second biasing member charges thefirst biasing member when the mirror is driven from the first positionto the second position.
 3. The image-taking apparatus according to claim1, further comprising a shutter, wherein the first cam charges theshutter when the charge portion charges the second biasing member. 4.The image-taking apparatus according to claim 1, further comprising ashutter, wherein the second biasing member drives the shutter from acharged state to a state in which the release of the charge is allowedwhen the second biasing member drives the mirror from the first positionto the second position.
 5. The image-taking apparatus according to claim1, further comprising a driven member, which includes the holding memberand is driven by the second biasing member in a state in which thedriven member is coupled to the mirror by the holding member.
 6. Theimage-taking apparatus according to claim 5, further comprising ashutter, wherein the driven member drives the shutter.
 7. Theimage-taking apparatus according to claim 1, wherein the first andsecond cams are driven in the same direction.
 8. The image-takingapparatus according to claim 1, wherein the first and second cams arerotated and driven around the same axis.
 9. An image-taking apparatuscomprising: a mirror, which is movable with respect to an optical path;a mirror drive member, which is movable to a first position at which themirror is disposed in the optical path and to a second position at whichthe mirror is retracted outside the optical path; a first biasingmember, which produces biasing force for driving the mirror drive memberfrom the second position to the first position; a shutter; a shutterdrive member, which drives the shutter; a coupling member, which isprovided on the shutter drive member and couples the mirror drive memberto the shutter drive member; a second biasing member, which producesbiasing force for driving the shutter drive member and drives the mirrordrive member from the first position to the second position via theshutter drive member and the coupling member; a first cam, whichincludes a charge portion for driving the shutter drive member in adirection in which the second biasing member is charged and a releaseportion for allowing the drive of the shutter drive member by the secondbiasing member; a second cam, which releases the coupling of the mirrordrive member by the coupling member at the second position; and a motor,which drives both of the first and second cams, wherein the motor drivesthe first and second cams only in one direction.
 10. An image-takingapparatus comprising: a mirror, which is movable to a first position atwhich the mirror is disposed in an optical path and to a second positionat which the mirror is retracted outside the optical path; a firstbiasing member, which produces biasing force for driving the mirror fromthe second position to the first position; a second biasing member,which produces biasing force for driving the mirror from the firstposition to the second position; an engaging member, which engages withthe mirror to prevent the drive of the mirror by the first biasingmember; a first cam, which includes a charge portion for charging thesecond biasing member and a release portion for releasing the charge ofthe second biasing member; and a second cam, which releases theengagement of the engaging member with the mirror, wherein the secondcam causes the engaging member to retract from the mirror when themirror and the engaging member are relatively moved toward a position atwhich their engagement is allowed.
 11. The image-taking apparatusaccording to claim 10, further comprising a motor, which drives both ofthe first and second cams, wherein the motor drives the first and secondcams only in one direction.
 12. The image-taking apparatus according toclaim 10, wherein the second biasing member charges the first biasingmember when the mirror is driven from the first position to the secondposition.
 13. The image-taking apparatus according to claim 10, furthercomprising a shutter, wherein the first cam charges the shutter when thecharge portion charges the second biasing member.
 14. The image-takingapparatus according to claim 10, further comprising a shutter, whereinthe second biasing member drives the shutter from a charged state to astate in which the release of the charge is allowed when the secondbiasing member drives the mirror from the first position to the secondposition.
 15. The image-taking apparatus according to claim 10, furthercomprising a drive member, which includes the engaging member andtransmits the biasing force of the second biasing member to the mirrorvia the engaging member.
 16. An image-taking apparatus comprising: amirror, which is movable to a first position at which the mirror isdisposed in an optical path and to a second position at which the mirroris disposed outside the optical path; a first biasing member, whichproduces biasing force for driving the mirror from the second positionto the first position; a shutter; a shutter drive member, which drivesthe shutter; an engaging member, which is provided for the shutter drivemember and engages with the mirror; a second biasing member, whichproduces biasing force for driving the shutter drive member and drivesthe mirror from the first position to the second position via theshutter drive member and the engaging member; a first cam, whichincludes a charge portion for driving the shutter drive member in adirection in which the second biasing member is charged and a releaseportion for allowing the drive of the shutter drive member by the secondbiasing member; and a second cam, which releases the engagement of theengaging member with the mirror that has been moved to the secondposition, wherein the second cam causes the engaging member to retractfrom the mirror when the shutter drive member is driven by the chargeportion to a position at which the engagement of the engaging member andthe mirror that has been moved to the first position is allowed.
 17. Theimage-taking apparatus according to claim 16, further comprising amotor, which drives both of the first and second cams, wherein the motordrives the first and second cams only in one direction.